The MOSFET is perhaps the most manufactured semiconductor device in history. The MOSFET is a fundamental building block in any integrated circuit. From logic circuits to memory, the MOSFET is simply indispensable.
In simplest terms, the MOSFET is a three terminal device with electrical contacts leading to a source, a drain, and a gate. The source and the drain are formed in a semiconductor substrate by doping. The gate is formed between the source and drain atop the substrate (separated by a thin gate oxide). Electrical contacts to the "outside world" are then required for the source, drain, and gate.
While this basic MOSFET structure has been known for decades, with the shrinking of the MOSFET device down to deep submicron dimensions, it has become increasing difficult to form the source and drain electrical contacts reliably over the source and drain regions (which are typically formed self-aligned to the gate).
What is needed is a method for forming a MOSFET with self-aligned source and drain contacts.